Yer looking to make some shafts?
If so, Mase, AZ name, (Roy Mason) in Canada has a nice stock of ash shaft wood that came from the Dufferin Factory.
I bought some decent ones from him. I don't know what he has on hand but maybe he can even fix you up with the squares or dowels.
Mine had a bit of a taper when I received them.
He reads the threads a bit so a good chance that he will see this anyway.